1. Field of the Invention
The present invention relates to a portable, rail cutting apparatus.
2. Description of the Related Art
During the laying of railroad tracks or the joining of railroad track sections, rails may often need to be cut to specified lengths. Moreover, during railroad repairs, worn or damaged track sections may need to be cut out and replaced with new rails. These rails or track sections are generally cut by a powered rail cutting saw.
Typically, rail cutting saws employ a rotating cutting blade, such as, an abrasive rotary disk, which is applied directly to the rail to effect the desired cut. The rail cutting saw is powered by a motor, such as, for example, an internal combustion engine, which drives the cutting blade via a drive assembly.
To provide support and stability, as well as effectively guide the saw over the intended cutting area, rail cutting saws may also be configured to cooperate with a rail-mounted guide assembly. Generally, rail-mounted guide assemblies are arranged with a saw support portion and a rail mount portion. On the saw support portion, the assembly attaches to the body of the rail saw proximately along the center line between the drive pulley and the driven pulley. On the rail mount portion of the guide assembly, the assembly either clamps, joins, or otherwise secures the rail saw to the rails.
The drive assembly that drives the cutting blade, typically comprises a loop drive belt arrangement having one end of the belt coupled to a drive pulley, engaged by an output shaft of the motor. The other end of the belt is coupled to a driven pulley that engages the cutting blade. Generally, the driven pulley is coupled to the motor housing via a sliding support arm arrangement. The sliding support arm arrangement overlaps the fixed motor housing and, when the portions are not fastened together, the sliding portion is arranged to laterally slide relative to the fixed motor housing.
The sliding portion of the support arm arrangement supports the driven pulley while the fixed portion is the motor housing. The two portions are kept in place and prevented from sliding by fasteners that secure the two portions to each other. Upon loosening or removing the fasteners, the sliding portion is capable of laterally sliding in towards the motor housing or sliding out towards the driven pulley.
After a period of normal use, the loop drive belt may become loose. As such, rail saws may also be equipped with a manual belt tensioning system that enables the user to manually adjust the tension on the loop drive belt. Some belt tensioning systems comprise a tensioning screw that is positioned close to the center line between the drive and driven pulleys. In this belt tensioning system, the sliding support arm fasteners are first loosened or removed so that, as the tensioning screw is manually tightened, the sliding support arm arrangement slides or laterally extends out to increase the lateral distance between the drive pulley and the driven pulley. The increased distance serves to tighten the loop drive belt.
Other belt tensioning systems comprise a cam adjustment device, in which a cam structure and a post structure are positioned on the sliding support arm arrangement. With the sliding support arm fasteners loosened or removed, the cam portion is rotated to impart a tensioning force on the post structure that serves to slide or laterally extend the sliding support arm arrangement to increase the lateral distance between the drive pulley and the driven pulley, and thus, tighten the loop drive belt.
Rail cutting saws may also be equipped with an adjustable protective blade guard to reduce the risk of injury from flying debris and/or blade malfunction. In some instances, the blade guard may be kept in place by fasteners that require the use of tools to effect guard positional adjustments. That is, to adjust the guard position, the fasteners are manually loosened with the tool, the guard is rotated or pivoted into its new position, and then the fasteners are manually retightened with the tool to secure the guard in its new position.
In other instances, the blade guard may held in place by friction surfaces, thereby avoiding the use of tools to adjust the guard position. In this tool-less configuration, the friction surfaces are disposed at or near the pivot center of the blade guard and the blade guard position is adjusted by pushing or pulling a guard handle secured to the circumference of the blade guard. Attaching the handle to the circumference of the blade guard provides the mechanical advantage of facilitating the necessary torque to overcome the holding strength of the friction surfaces.